\[\left( x^{16}\ :x^{8} \right)\ :x^{4} \cdot x^{2} =\]
\[= x^{16 - 8}\ :x^{4} \cdot x^{2} = x^{8}\ :x^{4} \cdot x^{2} =\]
\[= x^{8 - 4 + 2} = x^{6}.\]